1. Field of the Invention
The present invention relates to a heating element which can be used as a rotating member for heating or a part thereof in a fixing device employed in an image forming device operated by an electrophotographic system, electrostatic recording system and other systems, that is, a fixing device which fixes, on a recording medium such as a recording paper sheet, a toner image formed in an image forming portion of the image forming device and transferred onto the recording medium by passing the recording medium (on which an unfixed toner image is held) through a nip formed by the rotating member for heating and a rotating member for pressurizing which is pressed against the rotating member for heating with heating under pressure, and further to a fixing device using such a cylindrical heating element.
2. Description of Related Art
Fixing devices employed in image forming devices operated by the electrophotographic system, electrostatic recording system or like system generally comprise a rotating member for heating 91 and a rotating member for pressurizing 92 which is pressed against the rotating member for heating 91, as shown in FIG. 22 as an example.
The rotating member for heating 91 is usually constituted by providing an elastic material layer 912 made of elastic material such as a silicon rubber around a hollow metal shaft 911 and disposing a heater H such as a halogen lamp heater inside the metal shaft 911. The elastic material layer 912 is covered with a fluorine-based wear-resistant film 913 in some cases.
The rotating member for pressurizing 92 is formed by providing an elastic material layer 922 around a shaft 921. The elastic material layer 922 is covered with a fluorine-based wear-resistant film 923 in some cases.
This type of fixing device is described in Japanese Unexamined Patent Publication Nos. H05-158369 (JP05-158369,A) and H05-210336 (JP05-210336,A).
However, in the above-mentioned conventional fixing device, the hollow metal shaft 911 having the heater H incorporated therein for the rotating member for heating 91 has large heat capacity because it is thickly formed so that it has sufficient strength as the shaft for the rotating member and for other reasons. Therefore, according to the heat-source portion comprising the hollow metal shaft 911 having the heater H incorporated therein, it takes much time to heat the surface of the rotating member for heating 91 to a temperature at which the toner image is fused with heating and is fixed onto the recording medium (a so-called warm-up time is long), and therefore it has been difficult to meet the demand for shortening the warm-up time of fixing devices for the ease of use of the devices and thus of image forming devices, and the recent demand for energy saving.